X-RAY TUBE ROTATING ANODE

The invention concerns an x-ray tube rotating anode, consisting of a base of a carbon a containing molybdenum alloy, e.g. TZM, as well as from a fuel course from where [fram and/or a Wolfram-Legierung, whereby the surface of the rotating anode is provided at least partly outside of the fuel course with a coat from one or more oxides or from a mixture from one or more metals with one or more oxides. A rotating anode with the production of X-ray supplied the electricity only to approximately 1% in x-ray energy one converts. The remaining 99% are converted into unwanted warmth, which leads to a strong temperature load of the rotating anode. In the past therefore at attempts, the heat energy produced in rotating anodes was not missing as rapidly as possible to exhaust predominantly by enlargement of the superficial Wärmeemissivität. Well-known measures are the stimulation of the rotating anode with graphite, with coats made of pulverized high-melting metals, like z “B. Titan or Tantal, from carbides, like e.g. titancarbide or tantalum carbide, or from oxide mixtures or oxide metal mixtures. The DE-OS 2443354 describes a rotating anode of the initially mentioned kind, with which the base, for example, is covered for TZM for the increase of the heat radiation ability with a Metalloxydsehicht from Aluminiumcxyd and titanium oxide. At-PS Nr.336143 describes likewise a rotating anode from a base made of high-melting metals, e.g. also from molybdenum alloys, which is provided outside of the fuel course with a coat layer from a composite material from molybdenum and/or tungsten and/or niobium and/or tantalum with oxide-ceramic materials such as TiO2 and/or A12 03 and/or ZrO2. In both prior publications carbon enthastende Moldbdän alloys were suggested as basic material and/or mentioned expressly. It had been recognized therefore due to these Vorver5ffentlichungen by the specialist obviously neither expected nor that with carbon containing molybdenum alloys, in particular with TZM, by means of a coat layer the expected suitable in other cases, while the usual life span lasting increase of the thermal radiation could not be achieved. The patent owner recognized rather for the specialist completely surprisingly that it comes with rotating anodes from a base from a carbon a containing molybdenum alloy, in particular from TZM, which are provided for the increase of the thermal radiation with a coat from oxides already to short period of operation of the rotating anode to a strong degradation of the originally good Emissionseigeuschaften. This feature might be supposed to attribute to a Kchlenstoff diffusion of the base into the outside oxide film. The negative influence on the heat radiation ability is nevertheless not understandably, when it is after the state of the art just as well-known and common, pure carbide layers, e.g. titancarbide, to apply for the increase of the thermal radiation on rotating anode bases. Bie of the invention at the basis lying task consists of creating a rotating anode for x-ray tubes of the initially mentioned kind from carbon containing molybdenum alloys with which independently of the actual working time a increased Wärmeemissivität is reached. This task is solved according to invention thereby that between bases and coat 10 to 200 m thick an intermediate layer from molybdenum and/or tungsten is arranged. The intermediate layer from molybdenum and/or tungsten otherwise already prevents one after short actual working time degradation of the heat emission characteristics of the rotating anode which can be observed. At the same time the intermediate layer represents an excellent adhesion mediator, thus to 4s that the coat layer well to the base sticks. Even on the assumption that Molybdänund serves/or tungsten intermediate layers as diffusion barrier for carbon, SE is the selection of these metals to that extent not obvious, when for relatives, very intensively examined and descriptive problem area, which applying focal spot courses made of high-melting metals on rotating anode bases from graphite, intermediate layers are needed as carbon diffuse ion barriers, on that however molybdenum and tungsten as less suitably to be valid and instead of its all rhenium and individual platinum metals, in addition, carbides, nitrides, oxides and Boride the tl, Zr, Hf, Nb and Ta than intermediate layer material be recommended. For the rotating anode base above all the molybdenum alloys TZM and TZC worked. The intermediate layer can be applied on the base cleaned by sandblast by common coating processes such as flaming wire syringes, flaming powder sprayings or by plasma spraying with layer thicknesses between 10 and 200, preferably between 40 and 50 btm. With smaller layer thicknesses than 10 btm the desired effect is not reached. Layer thicknesses of more than 200 m are uneconomically, there unnecessary for the desired effect in the manufacturing and affect the mechanical and thermal characteristics of the rotating anode mentioned unfavorably. The creation of the outside oxide film effected likewise favourable-proves by flaming powder sprayings or plasma spraying. It is favorable to accomplish after each of the two coatings a glow treatment under hydrogen atmosphere with 1600°C during a length of time of about 1/2 h. The unexpected technical progress with Anwendung' of the technical teachings gemfil the invention is more near described on the basis a diagram. Ti02 Beschicht. with Mo-intermediate layer on TZM Tl02 Beschicht. on TZM without ME intermediate layer 0,90 -- “O, o 0.70 r 0” 0.60 0.40 - a diagram, which shows the dependence of the thermal Emissivität on the number of the expositions (rotating anode bombardments with electron-beam, shows 0.30 0 100,200,300,400,500 number of the expositions Fig.1 dependence of the Emissivität on the number of the expositions Fig.1). Two rotating anodes of same dimensions are with one another compared once from a TZM base with a TiO - coating and once from a TZM base with a TiO2 - surface layer and a molybdenum intermediate layer. For the determination of the thermal emission coefficient the rotating anodes in an x-ray tube test stand in each case 500 expositions were exposed to a tube stream with one firing duration by 5,4 s during a tube tension of 81 kV and by 300 mA. Between the individual bombardments a cooling phase was kept of 5 min. After in each case 100 expositions over thermocouples the cooling curves of the rotating anodes were taken up, from which then by conversion the thermal emission coefficient could be determined. Both anodes exhibit a initial emission coefficient of about 0.9. With the rotating anode without Motybdän intermediate layer the EmissionskoeffiMent drops already after a small number of expositions strongly and oscillates themselves after approximately 500 expositions to a value around about 0.5. In contrast to it the emission coefficient with rising number of the expositions decreases only slightly and oscillates themselves after about 500 expositions with 0,83 with the rotating anode with molybdenum intermediate layer. It is to be recognized thereby clearly that by the intermediate layer according to invention a substantial technical progress is attainable, without, apart from slightly increased manufacturing costs, disadvantages must be taken in purchase.